Surface optimization of RBa2Cu3O7-delta (R = Y, Nd) epitaxial high T-c films for in situ photoemission studies

One of the intrinsic difficulties for in situ photoemission studies of high T-c oxide films is the surface volatility, especially the oxygen loss. In order to solve this problem, we have constructed a dedicated system for high T-c film surface studies, in particular for ARPES measurements. Here we briefly describe our pulsed laser deposition (PLD) system that is linked to the photoemission chamber at the Synchrotron Radiation Center (SRC) in Wisconsin, and discuss crystallographic and electronic properties measured on epitaxial YBa2Cu3O7-delta (YBCO) and NdBa2Cu3O7-delta (NBCO) films. Resistivity and XRD studies show that the best c axis epitaxial films, with T-c (onset) = 92 K (T-c0 = 90.5 K), are monophase and single crystalline with crystal coherence up to almost 1 mum. Initial core level photoemission study indicates that, for YBCO on SrTiO3 (without any buffer layer), the Ba oxide layer tends to be the dominant surface layer. Further experiments are underway to reproducibly detect sharp Fermi edge and perform ARPES study on optimally doped film surfaces.